1. Technical Field
The present invention relates generally to measurement for thermal pictures corresponding to infrared rays arising from subjects such as material or human bodies. In particular, this invention is concerned with a device for measuring temperature of a subject with an infrared array sensor capable of detecting a thermal picture from the subject, and a method for measuring temperature the subject entirely or locally by means of the device.
2. Related Art
Nowadays in various technical fields are widely being used thermal detection devices for sensing temperature from material or human bodies in response to even minute infrared rays.
For instance, a thermal detection device automatically turning on/off a lamp at gloomy spot and others, as shown in FIG. 1, is composed including pyroelectric sensor 10, amplifier (AMP) 11, low pass filter (LPF) 12, comparator 13, timer 14, driver 15, lamp 16 and light sensor 17.
In such a thermal detection device, pyroelectric sensor 10 accepts a minute infrared ray from for example a human body and generates an electric signal of low voltage corresponding to the infrared ray. Then, amplifier 11 operates to amplify the low-voltage electric signal up to an electric signal over a predetermined voltage.
During this, low pass filter 12 remove noises, e.g. high frequency noises, while amplifying the electric signal over the predetermined voltage.
Comparator 13 functions to compare the electric signal, which is higher than the predetermined voltage without high frequency noises, with reference voltage V_ref predetermined at for example 0.7V. If a compared result is higher than the reference voltage, timer 14 begins to operate.
Driver 15 supplies power toward lamp 16 to turn lamp 16 on during a definite time (e.g. 10 seconds) for which timer 14 is operating. Here, light sensor 17 generates an electric signal corresponding to light incident thereon in response to circumferential brightness, enabling or disabling an operation of comparator 13.
Summarily, the conventional thermal detection device shown in FIG. 1 operates with the aforementioned configuration such that pyroelectric sensor 10 enables lamp 16 to be automatically turned on when a person is closing thereto in a gloomy spot. In the thermal detection device shown in FIG. 1, as well known, pyroelectric sensor 10 employs a dielectric effecting having a pyroelectric effect. However, pyroelectric sensor 10 is disadvantageous upon which it is impossible to detect a material or human body standing without movement because it does not further generate any electric signal if infrared rays are continuously incident thereon.
To amend such shortness for thermal detection, there has been proposed another thermal detection device employing thermopile sensor 20, instead of pyroelectric sensor 10 of FIG. 1, as shown FIG. 2. Thermopile sensor 20 is a kind of thermal sensor mostly used for measuring a standing material or human body in a non-contacting mode.
Meanwhile, FIG. 3 shows that in recent years there is developing a thermopile array sensor (TAS) fabricated in a single module in which a plurality of thermopile sensors are arranged in square pixel array (e.g. 32×32).
The thermopile array sensors (TAS) are being adopted in advancing units for measuring thermal pictures of material or human bodies. A typical thermal picture measurement unit is shown in FIG. 4, which is composed including thermopile array sensor 30, amplifier (AMP) 31, low pass filter (LPF) 32, first analogue-digital converter (ADC) 33, second analogue-digital converter 34, digital signal processor 35 and display device 36.
Thermopile array sensor 30, for example, is formed of a module in which a plurality of thermopile sensors are arranged in square pixels to correspondingly detect temperature from respective parts (e.g. 32×32) of an subject. In addition, thermopile array sensor 30 includes temperature sensor TS, such as thermistor, for detecting internal temperature of the module.
Temperature sensor TS outputs an electric signal corresponding to internal temperature of the module. The thermopile sensors of thermopile array sensor 30 accepts infrared rays in the unit of pixel respectively from parts of an subject and then output electric signals corresponding each to the infrared rays.
Amplifier 31 operates to amplify the electric signals output from the thermopile array sensor 30. Low pass filter 32 removes high frequency noises from the electric signals. First analogue-digital converter 33 transforms the noise-removed electric signal from analogue component into digital component.
Second analogue-digital converter 34 transforms the electric signal, which is output from temperature sensor TS, from analogue component into digital component. Digital signal processor 35 outputs a difference from comparison between the digital signals transformed by first and second analogue-digital converter 33 and 34, computing temperature values of respective parts on the subject.
As an example, if internal module temperature detected by temperature sensor TS is 10° C. and temperature of a first part of the subject, which is detected by first pixel P(1,1) of thermopile array sensor 30 is 45° C., a thermal difference between them is calculated to determined the first part's temperature as being 35° C. As also, if temperature of a second part of the subject, which is detected by second pixel P(1,2) of thermopile array sensor 30 is 46° C. when internal module temperature detected by temperature sensor TS is 10° C., a thermal difference between them is calculated to determined the second part's temperature as being 36° C.
After generating a thermal picture corresponding to those thermal difference values respective to the parts of the subject, it is represented on display device 36, such as monitor or others, as exemplified in FIG. 4. Thereby, a user is able to identify a thermal distribution state of the subject or other thermal conditions thereof through the thermal picture represented on a monitor or other display unit.
However, in detecting thermal conditions only from specific parts of human body (e.g. forehead, ear, hand, or another part in human body) by means of the aforementioned thermal picture measurement units, it could be inconvenient on use because it is necessary to carefully adjust a distance and angle between a subject's part and the thermal picture measurement unit. If a distance and angle for measurement is unsuitably adjusted, it will result in a serious error in detecting temperature and/or thermal distribution from a subject.
In order to make a general thermopile sensor have a reasonable temperature value for thermal measurement by infrared rays, it needs to detect temperature from a sensor itself before obtaining a voltage output for temperature from a subject or target. In the conventional art, as it is assumed that a sensor's temperature is equal to its ambient temperature, the ambient temperature is used as the sensor's one. Referring to the arts disclosed in U.S. Pat. Nos. 5,012,813, 6,056,435, 6,299,347, 6,499,877, 7,314,309 and 7,787,938, a temperature sensor detecting its own temperature operates by the thermistor mode characterized in nonlinear log function, so that it could be slower in response rate and lower in accuracy of ambient temperature. Especially, since only one sensor was used for measuring its own temperature, it could be inevitable to result in lower accuracy on thermal detection.
Otherwise, in the former U.S. Pat. Nos. 5,012,813, 6,056,435, 6,299,347, 6,499,877, 7,314,309 and 7,787,938 was considered an ambient temperature value Ta applied to a conversion formula of core temperature Tc as the resultant bodily temperature in order to correct an actual bodily temperature in accordance with thermal variation of the circumference. However, in case ambient temperature goes down to be lower than 18° C., it should be additionally considered and corrected about thermal descent on the skin because an optical part as well as the sensor becomes lower in temperature and an operation amplifier of the system varies in thermal coefficient.
Furthermore, with the former U.S. Pat. Nos. 5,012,813, 6,056,435, 6,299,347, 6,499,877, 7,314,309 and 7,787,938, it was impossible to correct erroneous distance measurement arising from a non-contacting mode because it was just capable to accept one-channel (or one-pixel) information but the forms of array. Such one-pixel information cannot provide any way of finding out an actual distance from a subject to be detected. For instance, as disclosed in PCT/IB2006/003859, it needs an additional subsidiary for concentrating focuses onto a pair of light emission devices (LED). Moreover, the prior non-contacting measurement is incapable of detecting or correcting a shake or movement of a thermometer or subject, the reason of which is caused from that thermal data only by one pixel is insufficient to differentiate a subject's motion from a thermal variation.
In the meantime, the prior arts U.S. Pat. No. 7,787,938 and PCT/IB2006/003859 had to scan temperature by contacting a thermometer to a forehead or by spacing a thermometer out in a distance about 5 cm from a forehead in order to find a peak value of the skin around the forehead. This is because it inevitable to shift the thermometer toward a point of the highest temperature as a sensor has only one pixel. But, there are personal differences in distribution of temporal arteries, as like that the higher temperature point is found around a forehead, around a mouth, or at a temple. Consequently, the former technologies just provide means for scanning a forehead and the around thereof, being insufficient to scan and detect temperature from the whole face, so that it is difficult to exactly detect temperature from a person who has higher temperature at other facial points rather than his forehead.